SMD diode

[avc4eva]

Hi, I'm designing a PCB and am in need of a small package diode for protection from a small vibration motor.

Originally on breadboard i was using a 1N4001 so am now confused on what diode to use for smd, my project is constrained to space.
The Schematic designed is below and at the moment I'm using an SMA package diode but its rather large.



In short i am wondering what process i would need to determine an smd equivalent diode for this PCB and for future reference.

Thanks!

[tggzzz]

What are you protecting against?
What type of motor?

If it is reverse EMF/current from the motor, the diode should be across the motor. Assuming protecting from reverse EMF/current from the motor....

In general the calculation will be something along the lines of:

• when transistor switched off, the same current will continue to flow through the inductor and diode; hence the diode must be able to take that forward current
• energy stored in the inductor will have to be dissipated somewhere; that will be in the diode with a 0.6V drop, so you can work out how long the current will flow
• if you want faster dissipation then add a resistor in series with the diode, thus "increasing the 0.6V" to V=0.6+IR; choose R so that V does not damage the other components

You would be well advised to find application notes for drivers for the type of motor you are using

[avc4eva]

What are you protecting against?
What type of motor?

If it is reverse EMF/current from the motor, the diode should be across the motor. Assuming protecting from reverse EMF/current from the motor....

In general the calculation will be something along the lines of:

• when transistor switched off, the same current will continue to flow through the inductor and diode; hence the diode must be able to take that forward current
• energy stored in the inductor will have to be dissipated somewhere; that will be in the diode with a 0.6V drop, so you can work out how long the current will flow
• if you want faster dissipation then add a resistor in series with the diode, thus "increasing the 0.6V" to V=0.6+IR; choose R so that V does not damage the other components

You would be well advised to find application notes for drivers for the type of motor you are using

Thanks for the reply, just realized schematic is wrong anode should not be on the base but across motor, thanks for prompting me. And ye it's against reverse current. I will do what you said thanks!

[T3sl4co1l]

2N2222 won't draw any current that a common 1N4148 won't handle.

1N4148W, MMSD4148, etc. are common numbers.

Tim